PROJECT SUMMARY This Mentored Research Scientist Development Award (K01) will provide support for Dr. Christopher Morrison to develop the skills necessary to become an independent investigator examining environmental prevention strategies to reduce adolescent alcohol consumption and alcohol-related harms. Alcohol consumption by adolescents under 21 is an important public health problem because alcohol contributes to over 4,300 adolescent deaths every year and to increased risks for alcohol use disorders and other problems in later life. An integrated program of coursework, mentorship and research will allow Dr. Morrison to accomplish three training objectives: developing comprehensive expertise 1) in theory, data collection, and statistical analysis for social networks; 2) in research methods and statistical analysis for longitudinal and geographically referenced survey data, and 3) conducting research to assess exposure to social media as a determinant of alcohol consumption among adolescents. The research program comprises two complementary studies. The first is an innovative use of data from Waves I to IV of the National Longitudinal Study of Adolescent to Adult Health (Add Health), an ongoing longitudinal study of a school-based sample who were adolescents in 1994/95. Participants' alcohol consumption will be related to their friends' alcohol consumption, the characteristics and structures of their social networks, and characteristics of the neighborhoods in which they live (e.g. social disorganization, alcohol outlet density). The second study uses data from Healthy Communities for Teens (HCT), an ongoing study of 261 adolescents aged 14-16 years (R01-HD078415; PI: Byrnes, H) of neighborhood exposures and alcohol consumption. A follow-up data collection will assess participants' engagement with digital social media, their exposure to alcohol through digital social media, and the structure of their digital social networks. Study One, using Add Health data, will address two Specific Aims: 1) to build a multiscale and dynamic model of adolescents' alcohol consumption based on their location within a social network, the structure of the network, and other members' attitudes and behaviors towards alcohol, and 2) to assess interrelationships between social networks, neighborhood conditions, and alcohol consumption during adolescence, and the effects on alcohol consumption into young adulthood. Study Two, using HCT data, will address Aim 3) to test the differential effects of exposure to alcohol through in-person social networks and digital social networks on adolescent alcohol consumption. The short-term objective of the research is to identify the people through whom, the places where, and the in-person vs. digital platforms through which social networks most substantially influence adolescents' alcohol consumption. The overall career development program will provide critical support for Dr. Morrison to progress to independent scientist, conducting innovative studies of adolescents' alcohol consumption and their social and physical environments, and identifying areas for effective preventive intervention.